Weather resistant polyacetal composition

Abstract

A polyacetal resin composition comprises a polyacetal resin, (A) a light stabilizer selected from the group consisting of a benzotriazole compound, a benzophenone compound, an aromatic benzoate compound, a cyanoacrylate compound, and an anilide oxalate compound and (B) an aliphatic acid ester. It is improved in stability to weathing.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A polyacetal resin composition which comprises a polyacetal resin, (A) a light stabilizer present in an amount of 0.05-2 percent by weight, wherein said light stabilizer is a benzotriazole compound, (B) an aliphatic fatty acid ester obtained from a fatty acid and a polyalkylene glycol, wherein said aliphatic fatty acid ester is present in an amount of 0.1-5 percent by weight, and (C) a hindered amine which is a piperidine derivative, wherein said piperidine derivative is an adipate or sebacate derivative having sterically hindered groups, the combination of (A), (B) and (C) having a synergistic effect in terms of weathering stability. 
     
     
       2. A polyacetal resin composition as claimed in claim 1 wherein said polyacetal resin is a polyoxymethylene homopolymer or a polyacetal copolymer or terpolymer in which a main chain consists largely of polyoxymethylene chains. 
     
     
       3. A polyacetal resin composition as claimed in claim 1 wherein said benzotriazole compound is 2-(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl) benzotriazole, 2-(2'-hydroxy-3',5'-di-isoamyl-phenyl) benzotriazole, 2- 2'-hydroxy-3',5'-bis-(alpha,alpha-dimethylbenzyl) phenyl! benzotriazole, or 2-(2'-hydroxy-4'-octoxyphenyl) benzotriazole. 
     
     
       4. A polyacetal resin composition as claimed in claim 1 wherein said fatty acid is acetic acid, propionic acid, caproic acid, undecylic acid, pivalic acid, caprylic acid, lauric acid, tridecyl acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoserinic acid, cerotic acid, heptacosanic acid, montanic acid, melissic acid, lacseric acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, arachidonic acid, or erucic acid. 
     
     
       5. A polyacetal resin composition as claimed in claim 1 wherein the hindered amine compound is a piperidine derivative having sterically hindered groups. 
     
     
       6. A polyacetal resin composition as claimed in claim 5 wherein said hindered amine compound is 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-(phenylcarbamoyoxy)-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidyl) oxalate, bis(2,2,6,6-tetramethyl-4-piperidyl) malonate, bis(2,2,6,6-tetramethyl-4-piperidyl) adipate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethylpiperidyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) terephthalate, 1,2-bis(2,2,6,6-tetramethyl-4-piperidyloxy) ethane, bis(2,2,6,6-tetramethyl-4-piperidyl) hexamethylene-1,6-dicarbamate, bis(l-methyl-2,2,6,6-tetramethyl-4-piperidyl) adipate, or tris(2,2,6,6-tetramethyl-4-piperidyl) benzene-1,3,5-tricarboxylate. 
     
     
       7. A polyacetal resin composition as claimed in claim 6, wherein said benzotriazole compound is 2-(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-(2'-hydroxy-3',5'-di-isoamyl-phenyl) benzotriazole, or 2- 2'-hydroxy-3',5'-bis-(alpha,alpha-dimethylbenzyl)phenyl! benzotriazole. 
     
     
       8. A polyacetal resin composition as claimed in claim 3, wherein said hindered amine compound is bis(2,2,6,6-tetramethyl-4-piperidyl) adipate, or bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate. 
     
     
       9. The polyacetal resin composition as claimed in claim 7, wherein said benzotriazole compound is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. 
     
     
       10. The polyacetal resin composition as claimed in claim 7, wherein said benzotriazole compound is 2-(2'-hydroxy-3',5'-di-isoamyl-phenyl) benzotriazole. 
     
     
       11. The polyacetal resin composition as claimed in claim 7, wherein said benzotriazole compound is 2- 2'-hydroxy-3',5'-bis-(alpha,alpha-dimethylbenzyl)phenyl! benzotriazole. 
     
     
       12. The polyacetal resin composition as claimed in claim 8, wherein said hindered amine compound is bis(2,2,6,6-tetramethyl-4-piperidyl) adipate. 
     
     
       13. The polyacetal resin composition as claimed in claim 8, wherein said hindered amine compound is bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate. 
     
     
       14. The polyacetal resin composition as claimed in claim 1, wherein the light stabilizer is present in an amount of 0.1-1 percent by weight. 
     
     
       15. The polyacetal resin composition as claimed in claim 1, wherein the hindered amine is present in an amount of from 0.25-0.5 percent by weight. 
     
     
       16. A polyacetal resin composition as claimed in claim 1, wherein the fatty acid has 12 to 40 carbon atoms and the polyalkylene glycol has an average polymerization degree of 16 to 200.